1. Field of the Invention
The present invention relates to a semiconductor circuit, in particular, to a semiconductor circuit for use in various kinds of circuits such as a timer circuit, an oscillator circuit, or the like, which is formed by, for example, a CMOS circuit.
2. Description of the Related Art
For example, the Japanese patent laid-open publication No. JP-P2002-117671-A discloses not only a timer circuit but also a semiconductor memory including the timer circuit. In order to provide a timer circuit, a timer cycle of which tends to decrease as the temperature increases, and tends to increases as the temperature deceases, the timer circuit has the following configuration. A diode D has a temperature-dependent current characteristic, and a forward current of the diode D flows into an n type MOS transistor N1 that constitutes a primary side of a current mirror. A current flowing into a p type MOS transistor P2 and an n type MOS transistor N3 that constitute a secondary side of the current mirror is determined depending on the current flowing into the n type MOS transistor N1. The current flowing into the p type MOS transistor P2 and the n type MOS transistor N3 is supplied as an operating current of a ring oscillator which is constituted by inverters I1 to I3. Therefore, a cycle or period (timer cycle) of a clock signal CLK outputted from the present ring oscillator is influenced by the temperature characteristic of the diode D, so that the timer cycle decreases as the temperature rises.
However, in conventionally known timer circuits including the timer circuit disclosed in the Japanese patent laid-open publication No. JP-P2002-117671-A, there is such a problem that the circuit may stop operating when the power supply voltage itself is dropped.